Fundamentals of Cellular Calcium Signaling: A Primer.

Ionized calcium (Ca) is the most versatile cellular messenger. All cells use Ca signals to regulate their activities in response to extrinsic and intrinsic stimuli. Alterations in cellular Ca signaling and/or Ca homeostasis can subvert physiological processes into driving pathological outcomes. Imaging of living cells over the past decades has demonstrated that Ca signals encode information in their frequency, kinetics, amplitude, and spatial extent. These parameters alter depending on the type and intensity of stimulation, and cellular context. Moreover, it is evident that different cell types produce widely varying Ca signals, with properties that suit their physiological functions. This primer discusses basic principles and mechanisms underlying cellular Ca signaling and Ca homeostasis. Consequently, we have cited some historical articles in addition to more recent findings. A brief summary of the core features of cellular Ca signaling is provided, with particular focus on Ca stores and Ca transport across cellular membranes, as well as mechanisms by which Ca signals activate downstream effector systems.